This study aimed to investigate the effects of the argumentation-based inquiry (ABI) approach on the analytical thinking skills and academic achievement of seventh-grade students using a mixed method. It was conducted in a secondary school in the Western Black Sea region of Turkey with seventh-grade students from two classes during the fall semester of the 2021-2022 academic year. Unit-based achievement tests, analytical thinking scenarios, and semi-structured interviews were used as data collection tools. The findings show that the application of the ABI approach in science classes is effective in improving the academic achievement of students. According to the analytical thinking test findings, a significant difference was found in favor of the experimental group in the post-test. The evaluation of the quantitative and qualitative findings revealed that the ABI approach used in science lessons had improved the analytical thinking skills of the experimental group students.